package Demo1;

/**
 * 滚动数组
 */
class Solution2 {
    public int tribonacci(int n) {
        if(n == 0) {
            return 0;
        }else if(n == 1 || n == 2) {
            return 1;
        }
        int a = 0;
        int d = 0;
        int b = 1;
        int c = 1;
        for(int i = 3; i <= n;i++) {
            d = a + b + c;
            a = b;
            b = c;
            c = d;
        }
        return d;
    }
}